Yes! AVG free version 7.5 & above will work fine with 64 bit OS.
AVG 9.0 Should work fine with Windows 7 64 bit.
My personal opinion!
Throw away AVG free. Go with Avira Antivir (Free only)
Download & Install the following 3 freewares. It forms a free complete security suite for your system!
1. Avira Anvivir - http://www.free-av.com/en/download/index.html .
Avira is best & light solution for excellent overall system protection & internet security with real time updates, .